(06-06) 17:05 PDT EAST PALO ALTO -- East Palo Alto police have arrested a 17-year-old boy on suspicion of shooting a baby to death over the weekend in what investigators believe was a case of mistaken identity.

The teenager was out for revenge after being beaten up May 31 by Sureño gang members in Redwood City, police said at a news conference Monday.

About 1 a.m. Sunday, the teen thought he saw one of the gang members getting into a car on the 400 block of Wisteria Drive in East Palo Alto, said acting police Capt. Jeff Liu.

In the car, however, was a family of four leaving a baby shower who had nothing to do with the earlier fight, Liu said.

The suspect and one other young man walked up to the car and sprayed the front and back seats with small-caliber gunfire, killing 3-month-old Izak Jesus Garcia-Lopez and wounding the boy's parents, police said.

Izak's mother, Ivonne Garcia-Lopez, was in the back seat and threw her body in front of her 4-year-old son, Isaiah, and her baby. When the shooting stopped, she found that her leg had stopped a bullet possibly headed for Isaiah. Izak, though, had been shot in the head.

"He was such a precious angel," Garcia-Lopez, 28, said at the news conference, sobbing. "He is my everything. I was making my own little family and we were happy, and this person came into my life and destroyed it. They killed my baby and they killed part of my soul, too."

Garcia-Lopez's husband, 22-year-old Oscar Jimenez, was shot in the shoulder as he sat in the driver's seat. He is still hospitalized, but is expected to recover. His 4-year-old son was not hurt.

Police withheld the suspect's name because he is a juvenile. Liu said officers arrested him Sunday, after receiving tips from the community, at a house where he lives on the 400 block of Larkspur Drive in East Palo Alto - about a block from where the shootings happened.

A second boy, who is 16, was arrested at the house at the same time. Both were booked on suspicion of weapons violations, Liu said. Police found three weapons at the home, including a gun believed to have been the one used in the Sunday attack, Liu said.

Investigators later booked the 17-year-old on suspicion of murder after he "provided statements implicating himself," Liu said. The 16-year-old has not been booked in the shooting, "but we feel he was involved in it," Liu said.